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A detailed multi-scale investigation of the geotechnical, chemical and mineralogical properties was conducted on contaminated sediment samples collected within the Mar Piccolo, a marine basin in south of Italy. The basin is located close to one of the most important industrial sites in Europe also declared ‘at high risk of environmental crisis’ and prioritised for remediation activities. A multidisciplinary investigation campaign showed that the samples collected close to the seafloor are characterized by high values of both heavy metals and organic pollutants and by the presence of significant amount of organic matter. Several samples in the top layer exhibited peculiar geotechnical properties, in terms of plasticity and activity indexes, compressibility and hydraulic permeability. While the prime suspect for such unconventional behaviour was the chemo-mechanical coupling between soil skeleton and contaminants, it turned out that the biogeochemical degradation of organic matter and the presence of microfossils and diatoms is likely to affect significantly the micro to macro behaviour of polluted marine sediments., Géotechnique, 73 (6), ISSN:0016-8505, ISSN:1751-7656

Smectites, like other clay minerals, have been shown to promote ice nucleation in the immersion freezing mode and likely contribute to the population of ice-nucleating particles (INPs) in the atmosphere. Smectites are layered aluminosilicates, which form platelets that depending on composition might swell or even delaminate in water by intercalation of water molecules between their layers. They comprise among others montmorillonites, hectorites, beidellites, and nontronites. In this study, we investigate the ice nucleation (IN) activity of a variety of natural and synthetic smectite samples with different exchangeable cations. The montmorillonites STx-1b and SAz-1, the nontronite SWa-1, and the hectorite SHCa-1 are all rich in Ca2+ as the exchangeable cation; the bentonite MX-80 is rich in Na+ with a minor contribution of Ca2+, and the synthetic Laponite is a pure Na+ smectite. The bentonite SAu-1 is rich in Mg2+ with a minor contribution of Na+, and the synthetic interstratified mica-montmorillonite Barasym carries NH4+ as the exchangeable cation. In emulsion freezing experiments, all samples except Laponite exhibited one or two heterogeneous freezing peaks with onsets between 239 and 248 K and a quite large variation in IN activity yet without clear correlation with the exchangeable cation, with the type of smectite, or with mineralogical impurities in the samples. To further investigate the role of the exchangeable cation, we performed ion exchange experiments. Replacing NH4+ with Ca2+ in Barasym reduced its IN activity to that of other Ca-rich montmorillonites. In contrast, stepwise exchange of the native cations in STx-1b once with Y3+ and once with Cu2+ showed no influence on IN activity. However, aging of smectite suspensions in pure water up to several months revealed a decrease in IN activity with time, which we attribute to the delamination of smectites in aqueous suspensions, which may proceed over long timescales. The dependence of IN activity on platelet stacking and thickness can be explained if the hydroxylated chains forming at the edges are the location of ice nucleation in smectites, since the edges need to be thick enough to host a critical ice embryo. We hypothesize that at least three smectite layers need to be stacked together to host a critical ice embryo on clay mineral edges and that the larger the surface edge area is, the higher the freezing temperature. Comparison with reported platelet thicknesses of the investigated smectite samples suggests that the observed freezing temperatures are indeed limited by the surface area provided by the mostly very thin platelets. Specifically, Laponite, which did not show any IN activity, is known to delaminate into single layers of about 1 nm thickness, which would be too thin to host a critical ice embryo., Atmospheric Chemistry and Physics, 23 (8), ISSN:1680-7375, ISSN:1680-7367

Global warming in mid-latitude alpine regions results in permafrost thawing, together with greater availability of carbon and nutrients in soils and frequent freeze–thaw cycles. Yet it is unclear how these multifactorial changes will shape the 1 m-deep permafrost microbiome in the future, and how this will in turn modulate microbially-mediated feedbacks between mountain soils and climate (e.g. soil CO2 emissions). To unravel the responses of the alpine permafrost microbiome to in situ warming, we established a three-year experiment in a permafrost monitoring summit in the Alps. Specifically, we simulated conditions of warming by transplanting permafrost soils from a depth of 160 cm either to the active-layer topsoils in the north-facing slope or in the warmer south-facing slope, near the summit. qPCR-based and amplicon sequencing analyses indicated an augmented microbial abundance in the transplanted permafrost, driven by the increase in copiotrophic prokaryotic taxa (e.g. Noviherbaspirillum and Massilia) and metabolically versatile psychrotrophs (e.g. Tundrisphaera and Granulicella); which acclimatized to the changing environment and potentially benefited from substrates released upon thawing. Metabolically restricted Patescibacteria lineages vastly decreased with warming, as reflected in the loss of α-diversity in the transplanted soils. Ascomycetous sapro-pathotrophs (e.g. Tetracladium) and a few lichenized fungi (e.g. Aspicilia) expanded in the transplanted permafrost, particularly in soils transplanted to the warmer south-facing slope, replacing basidiomycetous yeasts (e.g. Glaciozyma). The transplantation-induced loosening of microbial association networks in the permafrost could potentially indicate lesser cooperative interactions between neighboring microorganisms. Broader substrate-use microbial activities measured in the transplanted permafrost could relate to altered soil C dynamics. The three-year simulated warming did not, however, enhance heterotrophic respiration, which was limited by the carbon-depleted permafrost conditions. Collectively, our quantitative findings suggest the vulnerability of the alpine permafrost microbiome to warming, which might improve predictions on microbially-modulated transformations of mountain soil ecosystems under the future climate., Science of The Total Environment, 807, ISSN:0048-9697, ISSN:1879-1026

The increasing atmospheric CO2 concentration is a consequence of human activities leading to severe environmental deteriorations. Techniques are thus needed to sequester and reduce atmospheric carbon. One of the proposed techniques is the transformation or construction of new soils into which more organic carbon can be sequestered and CO2 be consumed by increased weathering. By using a chronosequence of new and transformed soils on crushed limestone (0–48 years) in a Mediterranean area (Sicily), we tried to quantify the amount of organic carbon that could be additionally sequestered and to derive the corresponding rates. A further aim was to trace chemical weathering and related CO2 consumption and the evolution of macropores that are relevant for water infiltration and plant nutrition. Owing to the irrigation of the table grape cultivation, the transformed soils developed fast. After about 48 years, the organic C stocks were near 12 kg m-2. The average org. C sequestration rates varied between 68 and 288 g m-2 yr-1. The C accumulation rates in the transformed soils are very high at the beginning and tend to decrease over (modelled) longer time scales. Over these 48 years, a substantial amount of carbonate was leached and reprecipitated as secondary carbonates. The proportion of secondary carbonates on the total inorganic carbon was up to 50%. Main mineralogical changes included the formation of interstratified clay minerals, the decrease of mica and increase of chloritic components as well as goethite. The atmospheric CO2 consumption due to silicate weathering was in the range of about 44–72 g C m-2 yr-1. Due to the high variability, the contribution of chemical weathering to CO2 consumption represents only an estimate. When summing up organic C sequestration and CO2 consumption by silicate weathering, rates in the order of 110–360 g C m-2 yr-1 are obtained. These are very high values. We estimated that high sequestration and CO2 consumption rates are maintained for about 50–100 years after soil transformation. The macropore volume decreased over the observed time span to half (from roughly 10 to 5 %). The transformation of soils may even amend their characteristics and increase agricultural production. Due to the relatively sandy character, enough macropores were present and no substantial compaction of the soils occurred. However, great caution has to be taken as such measures can trigger deterioration of both soil ecosystem services and soil quality., Geoderma, 402, ISSN:0016-7061, ISSN:1872-6259

Bound to rock Organic matter binds to phyllosilicates, a process which affects both its transport and chemical stability. How does that affect the fate of terrestrial organic carbon that enters the ocean? Blattmann et al. show that organic carbon derived from soils is stripped from mineral surfaces upon discharge and dispersal into the ocean, whereas organic matter derived from ancient rocks is preserved there. Their results show that preservation of continentally derived organic matter in marine sediments is controlled largely by phyllosilicate mineralogy. Science , this issue p. 742

This is a post-peer-review, pre-copyedit version of an article published in Polar Biology. The final authenticated version is available online at: http://dx.doi.org/https://doi.org/10.1007/s00300-019-02588-z. Although cryptogamic covers are important ecosystem engineers in high Arctic tundra, they were often neglected in vegetation surveys. Hence we conducted a systematic survey of cryptogamic cover and vascular plant coverage and composition at two representative, but differing Arctic sites (Ny-Ålesund, Svalbard) along catenas with a natural soil moisture gradient, and integrated these data with physical–chemical soil properties. Soil samples were taken for comprehensive pedological and mineralogical analyses. Vegetation surveys were conducted based on classification by functional groups. Vascular plants were identified to species level. Correlation and multivariate statistical analysis were applied to determine the key environmental factors explaining vegetation patterns along the soil moisture gradients. We observed significant differences in gravimetric water, soil organic matter and nutrient contents along the moisture gradients. These differences were coincident with a shift in vegetation cover and species composition. While chloro- and cyanolichens were abundant at the drier sites, mosses dominated the wetter and vascular plants the intermediate plots. Twenty four vascular plant species could be identified, of which only six were present at both sites. Cryptogamic covers generally dominated with maximum areal coverage up to 70% and hence should be considered as a new additional syntaxon in future ground-truth and remote sensing based vegetation surveys of Svalbard. Multivariate analysis revealed that soil moisture showed the strongest relation between vegetation patterns, together with NH4–N and pH. In conclusion, soil moisture is a key driver in controlling cryptogamic cover and vegetation coverage and vascular plant species composition in high Arctic tundra.

Vast areas in the Mediterranean are characterised by evaporite deposits of the Messinian crises (c. 6–5.3 Ma BP). During this period, large deposits were built up in shallow lagoon-like systems and are now found in southern Italy, Albania, Cyprus and Turkey. So far, soil formation on evaporites has been studied predominantly in subarid to arid environments. Although the formation of soils has received new significance, little is known about the evolutional trajectories on evaporites of the Mediterranean. We therefore studied soil formation in the Caltanissetta basin (Sicily) where evaporites are most widespread. The lithologies included the sequence: marine clay deposits, laminated marl (diatomite; Tripoli sediments), Calcare di Base (limestone), detritic deposits, gypsum (selenite). The chemical signature (immobile elements, rare earth elements) indicated that they all have a similar origin. Surprisingly, both an increasing Corg and carbonate content in the soils caused a decrease in the δ 13C signal in carbonates and in part in the bulk soil. The low δ 13C and δ 18O values of carbonates in the parent material indicate a high rock-water (or meteoric water) interaction that has occurred during sedimentation and diagenesis. Organic matter was oxidised into the shallow lagoon-like systems and its carbon incorporated in the limestone. Elemental leaching from silicates during pedogenesis was most intense in the soils that developed on clays and Tripoli sediments. Vertisols and Mollisols have evolved, together with a high amount of oxyhydroxides (non-crystalline and crystalline forms) and kaolinite. Only weak soil formation was recognisable at sites having gypsiferous parent material. The presence of a high amount of selenite hindered a more advanced evolution. The soils developed on detritic and gypsiferous material exhibited some palygorskite that was inherited from the parent material. At sites having selenite or limestone, shallow Aridisols or Mollisols are found. Weathering is weakly pronounced, e.g. indicated by a high proportion of trioctahedral minerals. Besides inheritance from the parent material, smectite and kaolinite are also actively formed in the soils with increasing weathering. Plagioclase and mica are the main sources of smectite and K-feldspar is a main source of kaolinite neo-formation. The evaporite deposits vary greatly within short distances causing a high spatial diversity of soils. Consequently, soil quality strongly varies, which challenges agricultural use. Well-developed soil profiles and advanced weathering stages are only possible when marine clays, Tripoli sediments or detritic deposits are the parent material. Limestone (Calcare di Base) and gypsiferous sediments (selenite) strongly limit soil formation and mineral transformation.

Bentonites are rocks mostly consisting of swelling clay minerals. They were first described from the Cretaceous Benton Shale near Rock River, Wyoming, USA. Because of their useful properties (e.g. highly adsorbent, cation exchanging, swelling), bentonites have many uses, in industry (among them as drilling mud, purification agent, binder, adsorbent, paper production), culture (for e.g. pottery) and medicine/cosmetics/cat litter, civil engineering, and in the future even in the disposal of high-level nuclear waste. Particular chemical characteristics of bentonite clay minerals are rather variable but critically determine their suitability for a particular application. The 15 specialist authors discuss bentonite terminology, classification and genesis and use in eight chapters. Individual chapters deal with the methods bentonites are analysed with, their properties and performance in terms of parameters such as cation exchange capactiy, rheology, coagulation concentraion, water uptake capacity, free swelling, and electrical resistivity (amongst others). A chapter is dedicated to the sources of bentonites, the technology employed to produce them, and how quality control is carried out both in the mine and the laboratory. A further chapter is dedicated to methods of processing the mined material, different activation methods, drying, grinding, and purification. Use cases for bentonites are discussed in a chapter of its own. References, a section on norms and standards, and a list of abbreviations complete the text. The volume addresses students, researchers, and professionals in the mineral industry dealing with bentonite and their clay-mineral constituents, quality assessement and control, and persons that use bentonites in their products.

Sorption processes control the solubility of toxic thallium (Tl) in soils and thereby its potential leaching into groundwater or uptake by plants. Micaceous clay minerals and Mn oxides are considered to be key sorbents for Tl in soils. We studied the sorption and speciation of Tl in 36 geogenically Tl-rich topsoil materials from the Swiss Jura Mountains by combining chem-ical extractions, isotope exchange experiments, adsorption experiments, X-ray absorption spectroscopy (XAS), and sorption modelling. We demonstrate that the relation between exchangeable and soluble Tl determined in batch extractions of soils with only geogenic and with freshly spiked Tl matches adsorption isotherms of freshly spiked Tl, and that this relation can be described with a published 3-site cation exchange model for Tl adsorption onto illite. Complemented with XAS data, the results show that micaceous clay minerals control the short-term solubility of Tl via cation exchange, but also the long-term sequestration of most geogenic soil Tl (>90%) via structural fixation. Adsorption competition with K+ and NH4+ at the frayed edges of micaceous clay minerals greatly affects Tl solubility. Increases in the dissolved concentrations of K and NH4 in soil pore water may therefore lead to the release of Tl into solution. The fractions of geogenic Tl associated with Mn oxides were about half as high as the fractions of exchangeable Tl. This Mn-associated Tl is not readily mobilized by cation exchange, but could be released during periodic water logging and soil reduction. In (periodically) reducing environments, the potential of Mn oxides for long-term Tl sequestration is therefore limited. In conclusion, the results from this study high-light the importance of micaceous clay minerals for Tl cycling in soils and sediments, and suggest that concepts developed to assess the sorption of (radio)caesium onto micaceous clay minerals in soils and sediments are transferable to Tl., Geochimica et Cosmochimica Acta, 288, ISSN:0016-7037, ISSN:1872-9533

The major drawbacks of earth such as low water stability and moderate strength have led mankind to stabilize the earth. It has been developed as a vernacular technique in different civilizations. Since then, the focus was mainly on gypsum, lime, or pozzolan stabilization. Recently, cement has become one of the commonly used additives in earth stabilization, which consequently reduce the environmental advantage of earth. This paper deals with a reverse engineering approach for low environmental impact earth stabilization technique, aiming the replacement of cement in earth stabilization. Various earth-mixtures were done to investigate the performance of this technique. Water contact behaviour and compressive strength of the stabilized earth specimens was determined. Moreover, the characterization of the stabilization effect has been performed through X-ray powder diffraction patterns (XRD) and clearly identify the production of ettringite using very low CO2 intensive raw materials. Furthermore, the carbon footprint of the stabilized earth-mix has been determined with the help of LCA (life cycle assessment) calculation. The laboratory analyses on this mix-design have proven a high water-resistance and the results show a remarkable increase in compressive strength. Finally, these results open a new avenue for earth stabilization and secure the implementation of this material in the conventional construction industry., IOP Conference Series: Earth and Environmental Science, 588 (4), ISSN:1755-1315, ISSN:1755-1307

A synthesis of published and newly acquired stable and radiocarbon isotope data from soil, river, and marine particulate organic carbon (OC) from the South China Sea drainage and sedimentary basin reveals that OC derived from bedrock‐erosion (petrogenic OC) and marine productivity comprises the major contributors to bulk OC in particulate matter reaching abyssal depths, while soil‐derived OC appears negligible. Aluminum‐radiocarbon relationships of sediments suggest that soil OC initially associated with detrital terrestrial minerals is lost and replaced by marine OC during transport beyond the continental shelf. We estimate that petrogenic OC sinking to a ~30,000 km2 region of the deep northeastern South China Sea accounts for 0.6% of global petrogenic OC burial. The basin‐wide OC isotope patterns coupled with sediment trap observations highlight both the spatial variabilities of OC components as they propagate from source to sedimentary sink and the significance of petrogenic OC to deep ocean sediments., Geophysical Research Letters, 45 (17), ISSN:0094-8276, ISSN:1944-8007

Several barrier types are envisaged to minimize the release of radionuclides from waste matrices into groundwater. In a number of countries argillaceous rocks make up the natural barrier that will isolate radioactive substances from the aquifer. The present study addresses the influence of pore geometry as a limiting factor for anion diffusion in argillaceous rocks. Irrespective of the pore core size, anion diffusion can be limited by the pore-size opening, i.e. if the pore opening is so narrow that the electric double layers overlap and form a barrier to anions irrespective of the pore size. This so-called ‘bottleneck effect’ limits the anion diffusion. The present study extends previous investigations that focused on other factors which limit anion diffusion, e.g. mineralogy or interlayer equivalent pores. The existence of bottleneck pores was confirmed by effective tortuosity calculations and retention-potential measurements using mercury intrusion porosimetry. On the basis of two different core samples from argillaceous rocks from Switzerland, Opalinus Clay and Helvetic Marl, this work shows evidence of the existence of bottleneck pores. The larger permanent anion exclusion in the Helvetic Marl sample compared to the Opalinus Clay sample can be explained by the larger retention potential and larger effective tortuosity of the Helvetic Marl rock, which indicates more pores with bottleneck effects than is the case for the Opalinus Clay rock., Clays and Clay Minerals, 66 (4), ISSN:0009-8604, ISSN:1552-8367

The mineral-engineered barrier in the planned repository for radioactive waste in Switzerland is being designed as a granular bentonite mixture. The infiltrating pore water from the (clayey) host rock will start to resaturate the granular barrier after its emplacement. The discrete structure of the mineral barrier requires a more detailed analysis, because the porosity alone applied in the continuum approach cannot adequately describe the heat transfer. Towards this analysis, three granular size fractions have been arranged into square or hexagonal packings and considered in the heat transfer model presented in this paper. The six different granular arrangements are set either in a planar or in a cylindrical spatial system. A major feature of the approach is providing the modelled systems with an interstitial fluid of smoothly adjustable thermophysical parameters, approximating variable water contents. The effective thermal conductivity of various systems is an important output of the model. The calculation of the temperature equilibrium period directly depends on this parameter and represents a step towards a solution for the reliable determination of the resaturation timescale. The validity of the modelled effective thermal conductivities was confirmed by laboratory experiments on real granular bentonite.

The aims of this paper are to identify the driving mechanisms at the origin of the deflocculating action of inorganic dispersants and to study their consequences on the behaviour of a dense clay paste over time. Considering that the flow behaviour of clays is controlled by their surface charge, an extensive set of rheological experiments and zeta potential measurements are carried out. We first show that sodium hexametaphosphate disperses via electrostatic repulsive forces while sodium silicate acts through electrosteric repulsive forces. We show that this deflocculation can be achieved without reaching full coverage of positive charge with the dispersant. We then highlight that the stability of the deflocculated clay paste can be controlled by the proportion of introduced dispersant within the matrix. Finally, these results reveal that the re-arrangement of clay particles and the availability of residual positive charge are at the origin of the thixotropic behaviour and rigidification of the system over time.

The study of hard rock conversion into fine earths and clayey materials in the pedosphere is important in understanding the relative proportions of recent soil features to features that were inherited from ancient epochs. Cold environments are widely thought to be areas of physical weathering, but the coexistence of physical and chemical processes have also been shown. To further examine mafic rock (dolerite) weathering in soil environments and the conversion into clayey materials, Entic Podzols formed in the cold continental climate were studied. The key study was located in the central part of the flood basalt complex, or traps (traprocks), of the Central Siberian Plateau (Russia). The qualitative mineralogy was studied using X-ray diffraction and the quantitative mineral composition was determined using X-ray diffraction and subsequent Rietveld analysis. The micromorphological characteristics of the soils were studied in thin sections. Dolerite fragments and fine earths were sampled from soil profiles underlain by dolerite. XRD analyses indicated that pyroxene and especially plagioclase contents in the dolerite fragments and fine earths decreased from the bottom to the top soil horizons mostly in the mature soil profiles that were affected by chemical weathering of dolerite. The dioctahedral and trioctahedral smectites in the soils were inherited from a dolerite previously subjected to chemical weathering. The smectite was conserved in the inherited aggregates and protected against dissolution even in acidic soil horizons. Recent pedogenesis processes fractured individual fragments, converted it into soil micromass, and slightly decreased the total smectite content of the

Spatially discontinuous permafrost conditions frequently occur in the European Alps. How soils under such conditions have evolved and how they may react to climate warming is largely unknown. This study focuses on the comparison of nearby soils that are characterised by the presence or absence of permafrost (active-layer thickness: 2 – 3 m) in the alpine (tundra) and subalpine (forest) range of the Eastern Swiss Alps using a multi-method (geochemical and mineralogical) approach. Moreover, a new non-steady-state concept was applied to determine rates of chemical weathering, soil erosion, soil formation, soil denudation, and soil production. Long-term chemical weathering rates, soil formation and erosion rates were assessed by using immobile elements, fine-earth stocks and meteoric 10Be. In addition, the weathering index (K + Ca)/Ti, the amount of Fe- and Al-oxyhydroxides and clay minerals characteristics were considered. All methods indicated that the differences between permafrost-affected and non-permafrost-affected soils were small. Furthermore, the soils did not uniformly differ in their weathering behaviour. A tendency towards less intense weathering in soils that were affected by permafrost was noted: at most sites, weathering rates, the proportion of oxyhydroxides and the weathering stage of clay minerals were lower in permafrost soils. In part, erosion rates were higher at the permafrost sites and accounted for 79 – 97% of the denudation rates. In general, soil formation rates (8.8 – 86.7 t/km2/y) were in the expected range for Alpine soils. Independent of permafrost conditions, it seems that the local microenvironment (particularly vegetation and subsequently soil organic matter) has strongly influenced denudation rates. As the climate has varied since the beginning of soil evolution, the conditions for soil formation and weathering were not stable over time. Soil evolution in high Alpine settings is complex owing to, among others, spatio-temporal variations of permafrost conditions and thus climate. This makes predictions of future behaviour very difficult. This article is protected by copyright. All rights reserved.

The paper explores the concept of enhanced delivery of chemicals for soil improvement applications based on clay treatment by guanidinium salt solutions. This treatment is shown to cause significant increase in shear strength and decrease in the swelling potential of clayey soils, which are highly desirable results in many geotechnical applications. Whereas some other soil improvement techniques reduce soil permeability as a side effect, guanidinium increases permeability of pure bentonites and quartz–bentonite mixtures by an order of magnitude and maintains this increase under high confining stresses, thus enhancing its own and other agents' delivery. It is shown that molecular change of the clay minerals on the level of the surface chemistry results in an aggregation of small clay minerals to stable larger particles, thus providing a system of open pores. For a better understanding of the mechanisms behind the process of enhanced delivery, a simple analytical hydro-chemical model is developed and successfully validated against both experimental data from soil samples subjected to the flow of guanidinium solution and a more sophisticated numerical analysis. Potential applications of this technique to stabilisation of creeping landslides will be investigated in a companion paper.

Given shale's potential to serve as both a caprock for geological carbon sequestration and as the host for nuclear waste disposal, this study focuses on the structural characterization around a 1.5–3 m thick fault within the Opalinus Clay host rock and petrophysical characterization of both the host rock and fault core. Seven boreholes were drilled at the Mont Terri Rock laboratory in late 2018 to constrain the orientation of the so-called ‘Main Fault’ and several fracture families within the fault core using core and image logs. Contrary to typical fault models, matrix permeability and seismic velocity measurements show similarities in the host rock and within the Main Fault. In the clay-rich samples, measurements performed in laboratory at varying confining pressures indicate p-wave velocities range from 2.60 to 2.95 km/s perpendicular to foliation and 3.38–3.58 km/s parallel to foliation at near in-situ confining pressures, which increase with similar anisotropy at higher confining pressures (200 MPa). Since the permeability of the host rock and fault zone is very low (10−19–10−21 m2) flow is expected to prevail along fractures, where critical stress fault analysis suggests that potential hydraulically conductive fractures are actually conjugate to the Main Fault trend.

The city of Taranto in the south of Italy is one of the areas declared as &ldquo, at high risk of environmental crisis&rdquo, by the Italian government because it represents one of the most complex industrial sites in Europe, located near urban areas of high population density. The rich ecosystem of the Mar Piccolo basin, located at north of Taranto, started exhibiting unconfutable signs of environmental pollution, confirmed by the high concentrations of organic and inorganic contaminants. Among the different aspects involved in the environmental studies aiming at the basin remediation, this paper focuses on submarine sediments and reports some results of the geotechnical laboratory investigations which made also use of non-standard equipment and revised procedures for data interpretation in order to take account of the sediments&rsquo, contamination and heterogeneities. The geotechnical laboratory tests show that, despite the Mar Piccolo recent Holocene sediments having similar origin and composition to those of the Sub-Apennine clay basic formation, their behavioral facets appear to be altered by the presence of contaminants of both natural and anthropogenic origin. Results of washing tests are also presented as a first attempt to quantify the effects of chemo-mechanical coupling processes on the plasticity properties of the shallow sediments.

Mineral dust particles from deserts are amongst the most common ice-nucleating particles in the atmosphere. The mineralogy of desert dust differs depending on the source region and can further fractionate during the dust emission processes. Mineralogy to a large extent explains the ice nucleation behavior of desert aerosol, but not entirely. Apart from pure mineral dust, desert aerosol particles are often mixed with small amounts of biological material or particles exhibit a coating. Aging on the ground or during atmospheric transport can deactivate nucleation sites and thus strong ice-nucleating minerals may not exhibit their full potential. In the partner paper of this work, it was shown that mineralogy determines most but not all of the ice nucleation behavior in the immersion mode found for desert dust. In this study, the influence of semi-volatile organic compounds and the presence of crystal water on the ice nucleation behavior of desert aerosol in addition to mineralogy is investigated. This work focuses on the deposition and condensation ice nucleation modes at temperatures between 238 to 242 K of 18 dust samples sources from 9 deserts worldwide. Chemical imaging of the particles' surface is used to determine the cause of the observed differences in ice nucleation. It is found that while the ice nucleation ability of the majority of the dust samples is dominated by their quartz and feldspar content, in one carbonaceous sample it is mostly caused by organic matter, potentially cellulose and/or proteins. On the other hand, the ice nucleation ability of an airborne Saharan sample is found to be diminished likely by semi-volatile species covering ice nucleation active sites of the minerals. This study shows that in addition to mineralogy, other factors such as organics and crystal water content can alter the ice nucleation behavior of desert aerosol during atmospheric transport in various ways.

Recent soils from basic (amphibolite and meta-gabbro amphibolite) and ultrabasic (serpentinous dunite) rocks formed in cold and humid climates of Northern Eurasia (Russia) were studied to detail the characterization of soils and rocks with special attention to the interdependence of porosity system and rock mineralogy. The study plots were located in taiga and tundra zones of East Fennoscandia and the Polar Ural Mountains. A variety of methods was used including optical microscopy, X-ray diffraction and Rietveld analysis, and three supplemental methods for the determination of pore space characteristics in rocks: (i) mercury intrusion porosimetry, (ii) a modification of this method using the intrusion of a molten alloy (Wood's metal), and (iii) scanning atomic-force microscopy. The results illustrate that the specification of the porosity system is a significant factor in tracing the clay mineralogy in soils formed from hard rocks. Ultrabasic rock is the most sensitive to weathering, as determined by (i) the high value of small pores, especially those with a radius of Despite the presence of low proportions of phyllosilicates in both types of basic rocks, only soil from meta-gabbro amphibolite is enriched by clay minerals and is most probably affected by small pores (

The onset of dilation and uniaxial compressive strength (UCS) of rocks are known to be affected by mineralogical, petrographic and microstructural features. Therefore micro-textural variations are essential for understanding variation in strength and failure behaviour of rocks. In this study volcanic rock samples with different micro-textural characteristics from different locations in Turkey were evaluated. The mechanical tests revealed considerable variations in unconfined uniaxial compressive strength and the crack initiation (σCI) threshold. The UCS ranges between 108–289 MPa, and σCI ranges between 46–130 MPa. Detailed quantitative petrographic and mineralogical analyses were carried out on each tested specimen to understand these strength variations. Additionally, microstructural studies were carried out on thin sections before and after mechanical perturbation to analyze (1) the effect of the main constituents of the rock specimens and mineral heterogeneity on crack initiation and propagation, and (2) the orientation and distribution of micro- and macro-cracks formed during laterally unconfined compression. The synthesis of mechanical, mineralogical, petrographic and microstructural data suggests that both the crack initiation threshold and peak strength are influenced by the ratio of the area of fine grain groundmass (grains smaller than 200 μm) to amphibole and plagioclase phenocrysts. In addition σCI and UCS decrease with an increasing normalized area of biotite phenocryst.

We investigated the speciation and extractability of Tl in soil developed from mineralized carbonate rock. Total Tl concentrations in topsoil (0-20 cm) of 100-1000 mg/kg are observed in the most affected area, subsoil concentrations of up to 6000 mg/kg Tl in soil horizons containing weathered ore fragments. Using synchrotron-based microfocused X-ray fluorescence spectrometry (μ-XRF) and X-ray absorption spectroscopy (μ-XAS) at the Tl L3-edge, partly Tl(I)-substituted jarosite and avicennite (Tl2O3) were identified as Tl-bearing secondary minerals formed by the weathering of a Tl-As-Fe-sulfide mineralization hosted in the carbonate rock from which the soil developed. Further evidence was found for the sequestration of Tl(III) into Mn-oxides and the uptake of Tl(I) by illite. Quantification of the fractions of Tl(III), Tl(I)-jarosite and Tl(I)-illite in bulk samples based on XAS indicated that Tl(I) uptake by illite was the dominant retention mechanism in topsoil materials. Oxidative Tl(III)uptake into Mn-oxides was less relevant, probably because the Tl loadings of the soil exceeded the capacity of this uptake mechanism. The concentrations of Tl in 10 mM CaCl2-extracts increased with increasing soil Tl contents and decreasing soil pH, but did not exhibit drastic variations as a function of Tl speciation. With respect to Tl in contaminated soils, this study provides first direct spectroscopic evidence for Tl(I) uptake by illite and indicates the need for further studies on the sorption of Tl to clay minerals and Mn-oxides and its impact on Tl solubility in soils.

The continuous development of chemical additives facilitated the successful application of the earth pressure balanced (EPB) method in numerous tunnel-excavation projects. One major issue f...

Journal of Materials Research, 23 (4), ISSN:0884-2914, ISSN:2044-5326

Pore space issues and mineral paragenesis of traprocks from the central part of the basaltic province (Central Siberia, Russia) were studied, as was the fine size fraction ( The methods used included mercury intrusion porosimetry (MIP), impregnation of connective pores with a molten alloy (Wood's metal) combined with subsequent electron microscopy, optical microscopy, X-ray diffraction, and IR spectroscopy. Rock from the lithic contact is represented by slightly weathered dolerite and shows a tendency to bimodal pore size distribution with a second maximum in pore size at 10 nm, which is due to the occurrence of phyllosilicates. Coarse pore systems are mainly due to cracks, which allow an easy exchange of water. Higher total porosity in the rock in one of two pits (~ 12 vol.% compared with 4 vol.%) appears to be a prerequisite for the formation of a deeper and more mature profile. Secondary products of dolerite weathering are smectites determining the association of clay minerals in both soil profiles and Fe-oxides. Most likely, desegregation and weathering of the rock fragments from soil horizons are fast enough to keep sufficient amounts of smectite only in the fine size fraction of the shallow profile. In the mature profile, pedogenesis leads to acidification of upper soil horizons and to a pronounced decrease in the smectite proportion, not only in the soil but also in the rock fragments from soil horizons. Thus, smectite(s) that was stable in early stages of rock weathering and soil formation and became unstable due to soil acidification illustrates the metastable nature of clay mineralogy in the well-drained soils from basic rock.

This correction stands to the correct a spelling error to contributor name: Karin Glaser. The author group and the publisher wish all to recognize the name as Karin Glaser and not the former. The original article has been corrected.

The use of soil conditioners during excavation with earth pressure balance machines offers a number of advantages, including increased advancing rates, higher safety and settlement minimisation in a variety of ground conditions. Dispersing polymers and foams are added to optimise the strength and improve the deformation properties of the supporting soil paste. In this paper, possible effects of some commercially used products on clays are discussed. Whereas for most clays conditioning is based on lubrication (leading to reduced shear strength), for calcium bentonite a high polymer dosage can lead to the counterproductive effect of increasing the material's strength. In the case of kaolin, the change of mechanical behaviour is much more dramatic than simply reducing the strength; instead, the soil transforms into a viscous material with both liquid and solid properties. This unexpected phenomenon is characterised in detail and the working mechanisms of the used dispersants are identified. Shear-strength measurements at different polymer concentrations, with different kaolins and commercial clay dispersants are presented. The results suggest an enhanced particle-lubrication mechanism, arising from ion exchange and altered electrostatic forces between the clay surfaces and the surrounding water layer; this picture is confirmed by additional adsorption and microscopic measurements.

Bentonite is a potential material for use in the engineered barrier of radioactive waste repositories because of its low hydraulic permeability, self-sealing capability and retention capacity. It is expected that bentonite would react at the elevated temperatures accompanying the radioactive decay in the nuclear waste. The presented study was started in order to improve understanding of the coupled influence of temperature and (pore) water on the physicochemical and mineralogical properties of bentonite during thermal treatment under near-field relevant conditions. Granular Na-bentonite MX-80 was differently saturated (Sr= 1–0.05) and stored at different temperatures (50–150°C) in a closed system. Upon dismantling after different periods of time (3 to 18 months), mineralogical characteristics, cation exchange capacity and content of leachable cations, as well as physicochemical properties such as surface area and water adsorption were investigated.The results showed a high mineralogical stability. A slight conversion from the sodium to an earth alkali form of the bentonite was observed. However, considerable changes in the physicochemical properties of the bentonite were observed, particularly by treatment above the critical temperature of 120°C. The cation exchange capacity decreased during heating at 150°C by approximately. 10%. The specific surface area dropped by more than 50%. The water uptake capacity under free swelling conditions showed a slight tendency to lower values especially for samples heated for more than 12 months. The water vapour adsorption ability in contrast drops by 25% already within three months at T = 120°C. These changes are mostly related to the variations in the interlayer cation composition and to smectite aggregation processes. The observed alterations are rather subtle. However, temperatures ⩾ 120°C had a remarkable negative influence on different properties of MX-80.

Clogging of streambeds by suspended particles (SP) can cause environmental problems, as it can negatively influence, e.g., habitats for macrozoobenthos, fish reproduction and groundwater recharge. This especially applies in the case of silt-sized SP. Until now, most research has dealt with coarse SP and was carried out in laboratory systems. The aims of this study are to examine (1) whether physical clogging by silt-sized SP exhibits the same dynamics and patterns as by sand-sized SP, and (2) the comparability of results between laboratory and field experiments.We carried out vertical column experiments with sand-sized bed material and silt-sized SP, which are rich in mica minerals. In laboratory experiments, we investigated the degree of clogging quantified by the reduction of porosity and hydraulic conductivity and the maximum clogging depth as a function of size and shape of bed material, size of SP, pore water flow velocity, and concentration of calcium cations. The SP were collected from an Alpine sedimentation basin, where our field experiments were carried out. To investigate the clogging process in the field, we buried columns filled with sand-sized quartz in the stream bed.We found that the maximal bed-to-grain ratio where clogging still occurs is larger for silt-sized SP than for sand-sized SP. The observed clogging depths and the reduction of flow rate through the column from our laboratory experiments were comparable to those from the field. However, our field results showed that the extent of clogging strongly depends on the naturally-occurring hydrological dynamics. The field location was characterized by a more polydisperse suspension, a strongly fluctuating water regime, and high SP concentrations at times, leading to more heterogeneous and more pronounced clogging when compared to laboratory results., Water Research, 126, ISSN:0043-1354, ISSN:1879-2448

Earth pressure balance machines are increasingly being used for tunnelling in difficult soils and ground conditions. In clayey soils, clogging of the working tools is among the main hazards. Attempts to reduce this risk by adding anti-clogging chemicals do not always produce the desired effect. In this paper, the limited efficiency of the existing conditioning chemicals is quantified and explained, and an enhanced interaction mechanism is proposed. This mechanism is based on sealing the clay aggregates against the penetration of water; it requires the addition of polyamine chemicals, as a newly patented application. These chemicals have been shown to dramatically reduce the clogging potential of different clay pastes over a broad range of water contents, using novel approaches for quantifying the clogging behaviour of clays in general. These methods also establish important correlations between empirical stickiness and more fundamental soil parameters, and in particular the ratio between adhesion and strength. Together with microscopic investigations and adsorption measurements, this provides insight into the working mechanism of the new chemicals at the particle level; it also highlights the differences between this mechanism and that of commercially used foams and polymers.

This paper presents a methodology for assessing mineral abundances of mixtures having more than two constituents using absorption features in the 2.1–2.4 μm wavelength region. In the first step, the absorption behaviour of mineral mixtures is parameterised by exponential Gaussian optimisation. Next, mineral abundances are predicted by regression tree analysis using these parameters as inputs. The approach is demonstrated on a range of prepared samples with known abundances of kaolinite, dioctahedral mica, smectite, calcite and quartz and on a set of field samples from Morocco. The latter contained varying quantities of other minerals, some of which did not have diagnostic absorption features in the 2.1–2.4 μm region. Cross validation showed that the prepared samples of kaolinite, dioctahedral mica, smectite and calcite were predicted with a root mean square error (RMSE) less than 9 wt.%. For the field samples, the RMSE was less than 8 wt.% for calcite, dioctahedral mica and kaolinite abundances. Smectite could not be well predicted, which was attributed to spectral variation of the cations within the dioctahedral layered smectites. Substitution of part of the quartz by chlorite at the prediction phase hardly affected the accuracy of the predicted mineral content; this suggests that the method is robust in handling the omission of minerals during the training phase. The degree of expression of absorption components was different between the field sample and the laboratory mixtures. This demonstrates that the method should be calibrated and trained on local samples. Our method allows the simultaneous quantification of more than two minerals within a complex mixture and thereby enhances the perspectives of spectral analysis for mineral abundances.

Desert dust is one of the most abundant ice nucleating particle types in the atmosphere. Traditionally, clay minerals were assumed to determine the ice nucleation ability of desert dust and constituted the focus of ice nucleation studies. Only recently some feldspar species were identified to be ice-active at much higher temperatures than clay minerals, redirecting studies to investigate the contribution of feldspar to ice nucleation on desert dust. However, so far no study has shown the atmospheric relevance of this mineral phase. For this study four dust samples were collected after airborne transport in the troposphere from the Sahara to different locations (Crete, the Peloponnese, Canary Islands and the Sinai Peninsula). Additionally, eleven dust samples were collected from the surface from nine of the biggest deserts worldwide. The samples were used to study the ice nucleation behavior specific to different desert dusts. Furthermore we investigated how representative ice nucleation on surface-collected dust is for that in the atmosphere by comparing to the ice nucleation activity of the airborne samples. We used the IMCA-ZINC set-up to form droplets on single aerosol particles which were subsequently exposed to temperatures between 233–250 K. Dust particles were collected in parallel on filters for offline cold stage ice nucleation experiments at 253–263 K. To help the interpretation of the results from the ice nucleation experiments the mineralogical composition of the dusts was investigated. We found that a higher ice nucleation activity in a given sample can be attributed at 253 K to the K-feldspar content present in this sample whereas at temperatures between 238–245 K it is attributed to the sum of feldspar and quartz content present. A high clay content on the other hand is associated with a lower ice nucleation activity of a sample. This confirms the importance of feldspar at T > 250 K and the role of quartz and feldspars determining the ice nucleation activities at lower T as found by earlier studies for monomineral dust surrogates. Furthermore, we find that milling may lead to a decrease in the ice nucleation ability of polymineral samples due to a change in mineralogical composition in the atmospherically relevant size fraction arising from the different hardness and cleavage of individual mineral phases. Comparison of our comprehensive data set to an existing desert dust parameterization confirms its applicability for climate models. Our results suggest that for an improved prediction of the ice nucleation ability of desert dust in the atmosphere, the modelling of emission and atmospheric transport of the feldspar and quartz mineral phases would be key while other minerals are only of minor importance.

A detailed characterization of the pore space is crucial for understanding of transport and element transfer in rocks. Here, the effect of differences in texture and content of secondary minerals on transport in pore systems was determined for two rocks of widespread occurrence, mid-ocean ridge basalts (MORB) and granites. Pore space characteristics were analyzed by Hg-porosimetry, intrusion of a molten alloy, and synchrotron-based X-ray tomographic microscopy. For evaluating the role of pore space characteristics for the prediction of diffusive transport, data on porosity, and the effective diffusion coefficient (D eff) were compared. Extended connective pore systems due to cracks and mineral dissolution are present in samples of both rocks, indicating high internal specific surface area. Uneven pore size distributions in altered MORB samples can be assigned to secondary minerals. Pore spaces determined by X-ray tomography, used to determine main direction of pores in the 3-D orthogonal system, suggest a slight anisotropy. In log–log plots, both rocks show roughly a linear dependence of D eff for H2O and compounds with comparable diffusivities (D2O, monovalent cations, and anions) on porosity, but at same porosity D eff is clearly higher in granitic than in basaltic samples. This difference is increasing with decreasing porosity, indicating that at low porosities the efficiency of element transport in basaltic samples is diminished, mainly inherited by the presence of small pores slowing down diffusion. The fact that diffusive transport in basaltic rocks is stronger dependent on porosity than in granitic rocks shows that also other rock characteristics such as pore size distribution and tortuosity of the pore network, highly affected by the alteration degree, can markedly affect transport and reactivity of pore solution.

Tunneling using the earth pressure balance machines method in clayey soils requires the addition of conditioning chemicals to reduce the torque moment of the machine and to guarantee a safe and economical excavation process. Injection of foams and polymers at the cutter head of the tunnel boring machine with subsequent remolding in the pressure chamber transforms the excavated material into a deformable soil paste with preferably low strength and adhesion. The soil becomes more compressible and can develop viscous properties, such that the pressure and rate dependency of the shear strength of the mixtures are of major importance for the proper design and analysis of the tunneling processes. In this paper, the results of vane shear strength measurements on various conditioned clays and clay-sand mixtures at various shearing velocities and applied pressures are presented and analyzed. The results clearly show the effects of the chemicals used and also point out the differences in their efficiency depending on the clay mineralogy. This allows for an improved understanding of the working mechanisms of the chemicals.

The calculation and measurement of the densities of smectites proved that calculation can lead to accurate values if the smectite d001-value, water content, molar mass of one formula unit, interlayer composition, and layer charge density are considered. The density measurement was supposed to be affected by accommodation of some He in micropores. The specific surface area determined by the common N2 adsorption is largely affected by micropores which in turn was used as proxy for microporosity. The investigated materials show a wide range of microporosities (5–65 % of the total porosity up to 50 μm). Micropores are supposed to result from the imperfect stacking of single TOT layers resulting in the quasi crystalline overlap region but they also result from partial access of the interlayer at the edges. Unfortunately, both types of microporosity could not be distinguished quantitatively. For measurement of the microporosity both N2 and CO2 adsorption were found to be suitable. The mesoporosity of bentonites also covers a significant range. One particularly mesoporous material was identified both by N2 adsorption and mercury intrusion. SEM investigation suggests the fibrous microstructure to be responsible for the extraordinary mesoporosity. For the characterization of the mesoporosity, N2 adsorption showed best resolution. The macroporosity may be classified according to the type of aggregates observable by SEM. The typical rose like arrangement of smectites results in 1 μm macropores and relict structures of the volcanic glass particles result in larger pores. The third type of macropore simply results from the relative arrangement of aggregates.

Bentonites are candidate materials for encapsulation of radioactive waste. The cation exchange capacity (CEC) has proven to be one of the most sensitive parameters for detecting changes in mineral properties in bentonite-alteration experiments. An interlaboratory study of CECs and exchangeable cations for three reference bentonite buffer materials that were used in the Alternative Buffer Material test (ABM) project in Aspo, Sweden, was conducted to create a suitable database. The present study focused on CEC accuracy and compared CEC methods where care was taken to prevent dissolution of soluble minerals such as calcite and gypsum. The overall quality of the CEC and exchangeable cation values measured using non-Cu-trien CEC methods were good, with CECs of 74–91±0.5–3.3 meq/100 g and exchangeable cation values of 22–61±1.2–3.9 meq/100 g Na+, 7–23±0.8–1.5 meq/100 g Mg2+, and 19–39±0.8–1.6 meq/ 100 g Ca2+. The precision was comparable to the standard Cu-trien method even for exchangeable Ca2+, although the laboratories used different solution/solid ratios and reaction-time parameters for Cu-trien which affect carbonate dissolution. The MX80 and Dep.CAN bentonite exchangeable Ca2+ values were more accurate than standard-Cu-trien values. Using the optimized methods of this study, MX80 and Dep.CAN exchangeable Ca2+ values averaged 20.2±1.6 and 38.8±1.4 meq/100 g which amounts to ~70% of the inflated Cu-trien values. A more complex analysis of the CEC data using different methods, anion analyses, and mineralogical analysis is necessary to obtain plausible and accurate CEC values. Even with a more complicated analytical procedure, the CEC and exchangeable cation values were still not accurate enough because of excess anions. Chloride, sulfate, and dolomite might have increased the exchangeable Na+, Mg2+, and Ca2+ values.

The research presented details on specific interactions of underivatized C60 as an aggregate suspension in water (termed nC60) with clay minerals (montmorillonite and kaolinite), and a synthetic layered double hydroxide LDH. Batch and 1-D flow-through column interactions were analyzed via UV/Vis spectroscopy, X-ray diffraction analysis, and transmission electron microscopy. Results indicate that nC60 suspended in water interacted with all the solid materials (‘clays’) studied. The LDH, with a net positive surface charge, has the greatest capacity to associate with the negatively charged nC60, capable of adsorbing 18% w/w. Column studies support sorption isotherm data, with LDH retarding nC60 transport > 30 times more, in relative terms, than montmorillonite or kaolinite. Findings suggest that specific material interactions are primarily dominated by available surface area and electrostatic interaction at charged surfaces. Intercalation was not observed. These results have implications not only for understanding fullerene transport in the subsurface, but also towards engineering effective barriers for safe storage and disposal.

Soils are the product of a complex suite of chemical, biological, and physical processes. In spite of the importance of soils for society and for sustaining life on earth, our knowledge of soil formation rates and of the influence of biological activity on mineral weathering and geochemical cycles is still limited. In this paper we provide a description of the Damma Glacier Critical Zone Observatory and present a first synthesis of our multi disciplinary studies of the 150-yr soil chronosequence. The aim of our research was to improve our understanding of ecosystem development on a barren substrate and the early evolution of soils and to evaluate the influence of biological activity on weathering rates. Soil pH, cation exchange capacity, biomass, bacterial and fungal populations, and soil organic matt er show clear gradients related to soil age, in spite of the extreme heterogeneity of the ecosystem. The bulk mineralogy and inorganic geochemistry of the soils, in contrast, are independent of soil age and only in older soils (>100 yr) is incipient weathering observed, mainly as a decreasing content in albite and biotite by coincidental formation of secondary chlorites in the clay fraction. Further, we document the rapid evolution of microbial and plant communities along the chronosequence.

Fungi were isolated from fine granitic sediments, which were collected at 15 sampling points within a 20 m x 40 m area in front of the Damma glacier in the central Swiss Alps. From the 45 fungal isolates grown on nutrient-rich agar media at 4 degrees C, 24 isolates were selected for partial sequencing and identification based on the small subunit ribosomal DNA. Sequencing data revealed that the isolated fungi represented three fungal phyla and 15 species. The weathering potential of 10 of the 15 fungal species was tested with dissolution experiments using powdered granite material (< 63 mu m). The results showed that the zygomyceteous species Mucor hiemalis, Umbelopsis isabellina and Mortierella alpina dissolved the granite powder most efficiently due to the release of a variety of organic acids, mainly citrate, malate and oxalate. In particular, the high concentrations of Ca, Fe, Mg and Mn in the solutions clustered well with the high amounts of exuded citrate. This is the first report on fungi that were isolated from a non-vegetated glacier forefield in which the fungi's capabilities to dissolve granite minerals were examined.

Stone columns are primarily used for the purpose of ground improvement in fine grained soils in order to reduce settlements and the risk of bearing failure. They are also designed to improve the drainage conditions in the ground and to accelerate the consolidation processes within the clay. However, smear and disturbing effects caused during the construction of stone columns result in degradation of consolidation performance in comparison with the theoretically ideal conditions. Model stone columns are constructed in-flight under 50 times gravity in centrifuge tests and the soil micro-structure in the vicinity of these columns is investigated by applying different methods, including environmental scanning electron microscopy and mercury intrusion porosimetry. The results of these tests confirm that smear and disturbance occur owing to stone column installation and the region influenced can be divided into three sections: a penetration zone (1) where the sand particles are squeezed through the clay; a smear zone (2) where the soil particles have experienced a significant reorientation; and a densification zone (3) where the structure of the clay does not appear to change, but compaction of the clay is measurable. The extremes of the disturbed zone around model stone columns are determined to extend to about 2·5 times the column radius.

Microbial fuel cell (MFC)-based sensing was explored to provide useful information for the development of an approach to in situ monitoring of substrate concentration and microbial respiration rate. The ability of a MFC to provide meaningful information about in situ microbial respiration and analyte concentration was examined in column systems, where Geobacter sulfurreducens used an external electron acceptor (an electrode) to metabolize acetate. Column systems inoculated with G. sulfurreducens were operated with influent media at varying concentrations of acetate and monitored for current generation. Current generation was mirrored by bulk phase acetate concentration, and a correlation (R(2)=0.92) was developed between current values (0-0.30 mA) and acetate concentrations (0-2.3 mM). The MFC-system was also exposed to shock loading (pulses of oxygen), after which electricity production resumed immediately after media flow recommenced, underlining the resilience of the system and allowing for additional sensing capacity. Thus, the electrical signal produced by the MFC-system provided real-time data for electron donor availability and biological activity. These results have practical implications for development of a biosensor for inexpensive real-time monitoring of in situ bioremediation processes, where MFC technology provides information on the rate and nature of biodegradation processes.

A toposequence of Holocene soils located between 1100–2400 m asl in the Italian Alps served as the basis for the following analyses: the weathering of limestone and dolomite, the calculation of mass balances, understanding the formation of pedogenic Fe and Al, the determination of soil mineral and clay mineral reactions and transformation and the measurement of accumulation and stabilisation mechanisms of soil organic matter. Leaching of carbonates is most intense at the lower elevations, although calcite and dolomite have a higher solubility at low temperatures. The pCO2 in the soil is higher at lower elevations and weathering is driven mainly by carbonic acids. At higher elevations, organic acids appear to determine the mineral transformations and weathering reactions to a greater extent. This suggests that two very different weathering regimes (carbonic and organic acid weathering) exist along the toposequence. The transformation of mica into vermiculite is the main process in both the clay and fine-earth fraction. Weathering of silicate minerals started even before the carbonates had been completely removed from the soils. The transformation mechanisms of silicate minerals in the A and O horizon at higher elevations was at least as intensive as that at the climatically warmer sites. The neoformation of pedogenetic clays at climatically cooler sites was slightly greater than that at the warmer sites. However, the formation rate of secondary Fe and Al phases was more pronounced at lower elevation, which means that this process seemed to be driven dominantly by carbonic acid (weathering of primary minerals). Soil organic matter (SOM) abundance in the mineral soil is nearly 15 kg/m2 at all sites and, surprisingly, no climate-driven effect could be detected. In general, the preservation and stabilisation of SOM was due to poorly crystalline Al and Fe phases and vermiculite, regardless of some variations in the composition of the parent material (varying calcite/dolomite ratio).

Aweathering sequence with soils developing on volcanic, trachy-basaltic parent materials with ages ranging from 100–115,000 years in the Etna region served as the basis to analyse and calculate the accumulation and stabilisation mechanisms of soil organic matter (SOM), the transformation of pedogenic Fe and Al, the formation and transformation of clay minerals, the weathering indices and, by means of mass-balance calculations, net losses of the main elements. Although the soils were influenced by ash depositions during their development and the soil on the oldest lava flow developed to a great extent under a different climate, leaching of elements and mineral formation and transformation could still be measured. Leaching of major base cations coupled with a corresponding passive enrichment of Al or Fe was a main weathering mechanism and was especially pronounced in the early stages of soil formation due to mineral or glass weathering.With time, the weathering indexes (such as the (K+Ca)/Ti ratio) tend to an asymptotic value: chemical and mineralogical changes between 15,000 and 115,000 years in the A and B horizons were small. In contrast to this, the accumulation of newly formed ITM (imogolite type materials) and ferrihydrite showed a rather linear behaviour with time. Weathering consisted of the dissolution of primary minerals such as plagioclase, pyroxenes or olivine, the breakdown of volcanic glass and the formation of secondary minerals such as ITM and ferrihydrite. The main mineral transformations were volcanic glass ➔ imogolite ➔ kaolinite (clay fraction). In the most weathered horizons a very small amount of 2:1 clay minerals could be found that were probably liberated from the inner part of volcanic glass debris. The rate of formation and transformation of 2:1 clay minerals in the investigated soils was very low; no major changes could be observed even after 115,000 years of soil evolution. This can be explained by the addition of ash and the too low precipitation rates. In general, soil erosion played a subordinate role, except possibly for the oldest soils (115,000 years). The youngest soils with an age b2000 years had the highest accumulation rate of organic C (about 3.0 g C/m2/year). After about 15,000 years, the accumulation rate of organic C in the soils tended to zero. Soil organic carbon reached an asymptotic value with abundances close to 20 kg/m2 after about 20,000 years. In general, the preservation and stabilisation of SOM were due to poorly crystalline Al- and Fe-phases (pyrophosphate-extractable), kaolinite and the clay content. These parameters correlated well with the organic C. Imogolite-type material did not contribute significantly to the stabilisation of soil organic matter. © 2007 Elsevier B.V. All rights reserved. Keywords: Soil formation; Kaolinite; Weathering indexes; Soil organic matter; Mediterranean region; Volcanic soils